1. Field of the Invention
This invention relates to a unidirectionally solidified anisotropic metallic composite body exhibiting high temperature transverse ductility and strength properties comprising a nickel-base refractory-metal-monocarbide-reinforced eutectic superalloy containing boron. A reinforcing phase of the eutectic superalloy, is an aligned carbide reinforcing fibrous phase, preferably one selected from the monocarbides of Ti, V, Cb, Zr, Hf, Ta, and their alloys or mixtures thereof.
Illustratively, more preferred Ni-base compositions contain about, on weight basis, 0.5-7.0% Re, less than about 0.8% Ti, and at least an amount in excess of an impurity amount of B. Embedded in the matrix is an aligned carbide reinforcing fibrous phase, preferably one selected from monocarbides of Ta, V and their alloys or mixtures thereof.
2. Description of the Prior Art
Nickel-base eutectics reinforced by refractory metal (Ti, V, Cb, Hf, Zr, Ta) monocarbides are described by Lemkey U.S. Pat. No. 3,528,808, Smashey U.S. Pat. No. 3,904,402, Tarshis et al. U.S. Pat. No. 3,799,769, Walter et al. U.S. Pat. No. 3,793,012, Walter U.S. Pat. No. 3,944,416 and Bibring et al. U.S. Pat. No. 3,871,835. In general, they disclose high strength superalloys obtained from aligned nickel-base fiber-reinforced structures. The focus of the strength improvements in their alloys is in directions parallel to the direction of fiber alignment and unrelated to the alloy characteristics required to provide adequate tensile and rupture ductility properties in directions off axis to the fiber alignment.
Illustratively, Smashey's U.S. Pat. No. 3,904,402, issued Sept. 9, 1975 (filed June 1, 1973) broadly describes eutectic nickel-base alloys containing rhenium and a carbide reinforcing fiber phase exhibiting improved high temperature stress-rupture properties. Smashey teaches the preferred use of 4-7% w/o vanadium for enhancement of carbide fiber as well as matrix strengthening, use of up to about 3% w/o molybdenum (however preferably omits the use of Mo), and the preferred use of about 2-4% w/o tungsten in nickel-base superalloys. Smashey summarily teaches the additive use of vanadium and the restrictive use of molybdenum and tungsten.
Recent evaluations of Smashey's alloys have illuminated a generally limiting brittle (non-ductile) transverse strength characteristic. For example tensile tests performed on specimens of Smashey's alloy Example 13 oriented perpendicular to the direction of fiber alignment have furnished the following data:
______________________________________ Transverse Tensile Test Data (As Solidified) Temp. 0.2% U.T.S. Elong. Composition (.degree.F.) Y.S. (ksi) (%) ______________________________________ Smashey's Alloy 1400 126 126 0.2 13, U.S. 1650 -- 85 0.04 3,904,403 1900 54 55 0.64 ______________________________________
The invention of this application discloses that boron additions to nickel-base refractory metal monocarbide reinforced superalloys markedly improves off-axis tensile and rupture ductility properties.